Thermal treatment equipment

ABSTRACT

Thermal treatment equipment for rapidly heating a SiC substrate having a diameter of several inches or larger to a temperature as high as 1200° C. or higher with a high in-plane evenness by heating a peripheral zone of a substrate using high frequency induction and by heating a central zone of the substrate using infrared lamps while the substrate and a stage thereof are covered with a shield plate.

BACKGROUND OF THE INVENTION

The present invention relates to thermal treatment equipment used in a manufacturing process in which a thermal treatment must be achieved in as short a time as possible, for example, by the process for activating thermal treatment after ion implantation of impurities into SiC.

After impurities such as phosphor or nitrogen have been ion implanted into SiC substrate, a thermal treatment at a temperature as high as 1500° C. or higher is necessary in order to generate an impurities activating carrier. For such thermal treatment, it has already been reported to use a resistive heating oven, however, such resistive heating ovens inconveniently take an unacceptably long time until a temperature rises to about 1500° C. or higher. Furthermore, a duration of approximately 30 minutes is required for an effective thermal treatment and inevitably Si evaporates from the SiC substrate surface, resulting in irregularities on the substrate surface. In addition, not only Si but also the impurities are evaporated, so the impurities ion implanted region exhibits an unacceptably high resistance value, and it is not possible to fabricate a normal SiC element. Thermal treatment using high frequency heating has also been reported, however, such method may lead to uneven temperature distribution since the substrate is heated from its peripheral zone. High-speed thermal treatment equipment and a method using an infrared lamp have also been employed. According to this method, the temperature can rise to about 1700° C. in one minute and evaporation of Si from SiC substrate surface restrained. While it is possible for this method to achieve the temperature rise in a desired short time by convergence of infrared rays for heating, application of this method is limited to thermal treatment of the SiC substrate having a size on the order of 1 cm². In other words, this method is not suitable for mass production of SiC elements. In view of such problem encountered by the method and equipment of well known art, there is a serious need for a thermal treatment equipment so improved that even a SiC substrate having a diameter of about 2 inches or larger can be heated to a desired high temperature in a short time with a practically even temperature distribution.

Kazuo Arai and Sadafumi Yoshida: “Principle and Application of SiC element” published by Ohmsha, p. 110.

SUMMARY OF THE INVENTION

As has been described above, the thermal treatment equipment relying on the infrared lamp of prior art cannot be used for mass production of the SiC element from the SiC substrate having a diameter of several centimeters or larger. While the thermal treatment method using the high frequency oven has already been proposed, this method results in that the temperature in the peripheral zone is relatively high while the temperature in the central zone is relatively low. Therefore, the temperature distribution becomes significant and, in the SiC substrate, an area in which the impurities are adequately activated and an area in which the impurities are not adequately activated appear in the SiC substrate. Eventually, the in-plane unevenness of the electric properties of the SiC element becomes so serious that such equipment cannot be used for mass production of or for industrialization of SiC elements.

In view of the problem as has been described above, it is a principal object of the present invention to provide a thermal treatment equipment improved so that a SiC substrate having a diameter of several inches or larger can be rapidly heated to a temperature as high as about 1200° C. or higher with a high in-plane evenness by heating a peripheral zone of a substrate using high frequency induction and by heating a central zone of the sample using infrared lamps while the substrate and a stage thereof are covered with a shield plate.

In the case of heating the substrate at a high temperature by infrared lamps used with a quartz column, the conventional equipment has been accompanied also with another problem such that various impurities generated from the substrate stage may cling to the quartz column and obstruct transmission of the infrared rays. In view of this problem, it is also an object of the present invention to provide a thermal treatment equipment improved so that a quartz plate is interposed between the substrate or the stage thereof and the quartz column and thereby various impurities generated from the stage of the substrate are prevented from clinging to the quartz column.

In the case of heating by the infrared lamp, the temperature of the substrate becomes higher in the central zone than in the peripheral zone, as illustrated by FIG. 1(A). In the case of heating by the high frequency wave heating, on the other hand, the temperature of the substrate becomes higher in the peripheral zone than in the central zone because the peripheral zone of the substrate is primarily heated as illustrated by FIG. 1(B). The temperature distribution can be substantially uniformized first by heating the substrate by simultaneously using both the infrared lamp and the high frequency wave as illustrated by FIG. 1(C).

The object set forth above is achieved, according to the present invention, by thermal treatment equipment comprising a vacuum chamber allowing thermal treatment to be carried out in vacuum or various gas atmospheres, an electrically conductive sample stage provided within the vacuum chamber, and a sample placed on the sample stage. A high frequency coil surrounds the sample stage, and an infrared generator, consisting of a single or plural infrared waveguide quartz column(s), is placed above and/or below the sample. An infrared lamp and a rotary elliptical reflector both placed on one end of the infrared waveguide quartz column, and a coaxial double-wall quartz tube is placed inside the high frequency coil so that cooling water may flow between this coaxial double wall quartz tube, wherein the infrared lamp is water or air cooled by cooling water or air flowing outside the infrared lamp in order to prevent the sample from being heated by the infrared lamp.

The present invention may be implemented also in various preferred manners. In the thermal treatment equipment according to claim 1, a quartz plate is interposed between the sample and the infrared waveguide quartz column as also described in claim 2. In the thermal treatment equipment according to claim 1 or 2, the sample and the sample stage are covered with a shield plate as described in claim 3.

In the thermal treatment equipment according to any one of claims 1 through 3, the sample stage is covered with an electrically conductive shield plate provided with a gap having a dimension in a range of about 1 mm to about 30 mm as described in claim 4.

In the thermal treatment equipment according to any one of claims 1 through 4, one or both of the sample stage and the shield plate is or are made of tungsten, molybdenum or tantalum as described in claim 5.

In the thermal treatment equipment according to any one of claims 1 through 4, one or both of the sample stage and the shield plate is or are made of carbon or SiC coated carbon as described in claim 6.

In the thermal treatment equipment according to any one of claims 1 through 6, the high frequency wave has a frequency less than about 50 kHz as described in claim 7.

In the thermal treatment equipment according to any one of claims 1 through 7, further comprising a mechanism adapted to adjust a distance between one end surface of the quartz column and the sample in a range from about 0.5 mm to about 20 mm as described in claim 8.

In the thermal treatment equipment according to any one of claims 1 through 8, further comprising a sample temperature control means adapted to measure a temperature of the sample stage or the sample itself by a pyrometer or a thermocouple and thereby control the voltage or current applied to the infrared lamp or the high frequency coil as described in claim 9.

In the thermal treatment equipment according to any one of claims 1 through 9, the quartz column is arranged in a tilted posture as described in claim 10.

In the thermal treatment equipment according to any one of claims 1 through 10, wherein said equipment is programmed so that the SiC substrate is heated from a room temperature to about 1200° C. or higher in from about 10 seconds to about 5 minutes, maintained at such temperature for about 10 seconds to about 10 minutes and thereafter the SiC substrate is cooled to a temperature lower than about 1200° C. in about 10 seconds to about 30 minutes as described in claim 11.

In, the thermal treatment equipment according to claim 11, said equipment is programmed so that the SiC substrate is previously heated to a temperature lower than about 1200° C., then heated from a room temperature to about 1200° C. or higher in about 10 seconds to about 5 minutes and thereafter cooled to a temperature lower than about 1200° C. in about 10 seconds to about 30 minutes as described in claim 12.

The present invention has a unique construction as has been described above and provides an effect as follows.

The thermal treatment equipment as defined in claim 1 comprises a vacuum chamber allowing thermal treatment to be carried out in vacuum or various gas atmospheres, an electrically conductive sample stage provided within the vacuum chamber, and a sample placed on the sample stage. A high frequency coil surrounds the sample stage, and an infrared generator consisting of a single or plural infrared waveguide quartz column(s) is placed above and/or below the sample. An infrared lamp and a rotary elliptical reflector are both placed on one end of the infrared waveguide quartz column, and a coaxial double-wall quartz tube placed inside the high frequency coil so that cooling water may flow between this coaxial double wall quartz tube. The infrared lamp is water or air cooled by cooling water or air flowing outside the infrared lamp in order to prevent the sample from being heated by the infrared lamp. Such equipment allows a temperature to rise from a room temperature up to about 1800° C. as rapidly as in about 1 minute and to ensure a temperature distribution having unevenness as negligible as ±50° C. without any anxiety of equipment destruction.

The thermal treatment equipment defined in claim 2 corresponding to the equipment according to claim 1, wherein a quartz plate is interposed between the sample and the infrared waveguide quartz column wherein the quartz plate prevents any impurities from clinging to the end surface of the infrared waveguide quartz column, so the infrared irradiation can be carried out for a long period without exchanging the infrared waveguide quartz column. The quartz plate is exchanged when it is desired.

The thermal treatment equipment defined in claim 3 corresponding the equipment according to claim 1 or 2, wherein the sample and the sample stage are covered with a shield plate which allows a temperature to rise up to about 1200° C. or higher rapidly.

The thermal treatment equipment defined in claim 4 corresponding to the equipment according to any one of claims 1 through 3, wherein the sample stage is covered with an electrically conductive shield plate provided with a gap having a dimension in a range of about 1 mm to about 30 mm is effective to prevent an induction heating by the high frequency wave and to restrain a temperature rise of the coaxial double quartz tube due to a temperature rise of the electrically conductive shield plate.

The thermal treatment equipment defined in claim 5 corresponding to the equipment according to any one of claims 1 through 4, wherein one or both of the sample stage and the shield plate are made of tungsten, molybdenum or tantalum is effective to prevent the shield plate from being molten even at a high temperature and thereby prevents the shield plate from changing from its initial shape.

The thermal treatment equipment defined in claim 6 corresponding to the equipment according to any one of claims 1 through 4, wherein one or both of the sample stage and the shield plate are made of carbon or SiC coated carbon which allows the thermal treatment to be stabilized even at a high temperature.

The thermal treatment equipment defined in claim 7 corresponding to the equipment according to any one of claims 1 through 6, wherein the high frequency wave has a frequency less than about 50 kHz promotes the high frequency wave to propagate into the sample so that a zone of the sample in the vicinity of its center can be sufficiently heated so as to minimize unevenness of the temperature distribution.

The thermal treatment equipment defined in claim 8 corresponding to the equipment according to any one of claims 1 through 7, further comprising a mechanism adapted to adjust a distance between one end surface of the quartz column and the sample in a range from about 0.5 mm to about 20 mm improve a heating effect of the infrared rays.

The thermal treatment equipment defined in claim 9 corresponding to the equipment according to any one of claims 1 through 8, further comprising a sample temperature control means adapted to measure a temperature of the sample stage or the sample itself by a pyrometer or a thermocouple and control the voltage or current applied to the infrared lamp or the high frequency coil to allow outputs of the infrared lamp and the high frequency wave to be controlled and, thereby, the temperature of the substrate to be controlled.

The thermal treatment equipment defined in claim 10 corresponding to the equipment according to any one of claims 1 through 9, wherein the quartz column is tilted to allow many quartz columns to be used and, thereby, the infrared irradiation area to be enlarged.

The thermal treatment equipment defined in claim 11 corresponds to the equipment according to any one of claims 1 through 10, wherein said equipment is programmed so that the SiC substrate is heated from a room temperature to about 1200° C. or higher in about 10 seconds to about 5 minutes, then maintained at such temperature for about 10 second to about 10 minutes and thereafter the SiC substrate is cooled to a temperature lower than about 1200° C. in about 10 seconds to about 30 minutes. With such an arrangement, a resistance value of the SiC substrate ion-implanted with impurities such as phosphor, nitrogen, aluminum or boron can be adequately lowered and, at the same time, evaporation of Si from the SiC substrate leading to the undesirable surface irregularities can be prevented. In this way, a high quality SiC element can be manufactured.

The thermal treatment equipment defined in claim 12 corresponds to the equipment according to claim 11, wherein said equipment is programmed so that the SiC substrate is previously heated to a temperature lower than about 1200° C., then heated from a room temperature to about 1200° C. or higher in about 10 seconds to about 5 minutes and thereafter cooled to a temperature lower than about 1200° C. in about 10 seconds to about 30 minutes. With such an arrangement also, a resistance value of the SiC substrate ion-implanted with impurities such as phosphor, nitrogen, aluminum and boron can be adequately lowered and, at the same time, evaporation of Si from the SiC substrate leading to the undesirable surface irregularities can be prevented. In this way, high quality SiC element can be manufactured.

These and other features, objects and advantages of the present invention will become apparent upon reading the following description thereof together with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 and FIGS. 1(A)-1(C) are a schematic drawing and aligned temperature graphs which illustrate the temperature distribution through a substrate using the system of the present invention;

FIG. 2 is a vertical cross-sectional view of the thermal treatment equipment according to the invention;

FIG. 3A is an enlarged vertical cross-sectional view of the shielding structure;

FIG. 3B is a top plan view of the shield shown in FIG. 3A;

FIGS. 4(1)-4(6) are schematic views which illustrate various placements of the infrared lamps;

FIG. 5 is a graph plotting the measured progression of temperature rise in a substrate having a diameter of about 2 inches with use of the high frequency heating alone; and

FIG. 6 is a graph plotting the measured progression of temperature rise in a substrate having a diameter of about 2 inches using both high frequency heating and infrared heating.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIGS. 1 and 1(A)-1(C) illustrate the temperature distribution appearing as a result of heating by the infrared heating and/or the high frequency heating. FIG. 1(A) illustrates the temperature distribution appearing as a result of the infrared heating alone. FIG. 1(B) illustrates the temperature distribution appearing as a result of the high frequency heating alone, and FIG. 1(C) illustrates the temperature distribution as a result of both the infrared heating and the high frequency heating. FIG. 2 is a sectional view of a thermal treatment equipment according to the invention. FIG. 3 illustrates an example of a shielding structure. While the illustrated shielding structure is made of tantalum, this shielding structure may be made also of tungsten, molybdenum, carbon or SiC coated carbon. FIG. 4 illustrates placement of the infrared lamps. As illustrated, a plurality of infrared lamps are placed above and/or below a sample stage. FIG. 5 is a graph plotting a measured progression of temperature rise in the substrate having a diameter of 2 inches with use of the high frequency heating alone, in which a solid line indicates the temperature in the central zone and the broken line indicates the temperature in the peripheral zone. FIG. 6 is a graph plotting a measured progression of temperature rise in the substrate having a diameter of 2 inches with use of both the high frequency heating and the infrared heating. In this graph, the progression of temperature rise having been measured until first approximately 50 seconds elapse indicates the result obtained by use of the infrared heating alone, and the progression of temperature rise having been measured thereafter indicates the result obtained by use of both the infrared heating and the high frequency heating. The solid line indicates the temperature in the central zone and the broken line indicates the temperature in the peripheral zone of the substrate.

In the following description, structural elements are identified by the following reference numerals:

REFERENCE NUMERALS USED IN THE DRAWINGS

-   -   1 infrared lamp     -   2 rotary elliptical reflector     -   3 infrared waveguide quartz column     -   3A end surface     -   4 vacuum chamber     -   5 cooling water canal     -   6 quartz tube     -   7 high frequency coil     -   8 vacuum pumping exhaust port     -   9 infrared waveguide quartz column rise and fall mechanism     -   10 sample stage     -   11 shield plate     -   12 sample     -   13 quartz plate     -   14 temperature sensor pickup port     -   15 infrared temperature sensor insertion port     -   16 gas introducing port     -   17 gas exhausting port     -   18 inlet     -   19 outlet     -   20 gap     -   21 opening     -   22 lid     -   23 temperature control

Referring to FIG. 2, infrared rays emitted from an infrared lamp 1 are collected by a rotary elliptical reflector 2, then guided through an infrared waveguide quartz column 3 to an end surface 3 a of the quartz column 3. A sample 12 and a sample stage 10 are irradiated with the infrared rays coming from the end surface of the quartz column 3. Void space is defined around the rotary elliptical reflector 2 and this void space is provided with an inlet 18 and an outlet of cooling water so that the reflector 2 may be water cooled. Alternatively, it is possible to construct the void space so that the water cooling may be replaced by air cooling. The sample stage 10, shown also in FIG. 1, must be formed of an electrically conductive material. According to the invention, this requirement is met by forming the sample stage 10 of a metallic material having a sufficiently high melting point to resist a predetermined high temperature, e.g., tungsten, molybdenum and tantalum. Alternatively, it is possible to form the sample stage 10 by high purity carbon substantially free from metallic impurities, e.g., titanium, vanadium, chromium, manganese, iron, cobalt, nickel or copper, or by high purity carbon from which nitrogen, boron, aluminum or phosphor each being apt to become N-type or P-type impurities was removed as perfectly as possible, or by carbon having its surface coated with SiC.

Heat conduction from the sample stage 10 heated by infrared rays causes the temperature of sample 12, such as the SiC substrate, to rise. On the other hand, inductive heating by high frequency wave is applied to a high frequency coil 7 from a high frequency oscillator and heats by induction the sample stage 10, thereby causing the temperature of sample 12 to rise through thermal conduction. In the case of the sample 12 which is electrically conductive, the sample 12 itself also is heated by an inductive heating effect by high frequency RF energy. A shield plate 11 is provided in order to restrain heat dissipation. If this shield plate 11 is made of electrically conductive material, the temperature of shield plate 11 itself would rise similarly to the sample stage 10 and heat the members surrounding the sample stage 10, such as the quartz tube 6 for cooling water, eventually leading to destruction by melting or fissure. To avoid such an undesirable result, shield plate 11 is made similarly to the sample stage 10 of a high melting point metallic material, such as tungsten, molybdenum or tantalum or high purity carbon or SiC coated carbon. A gap 20, as illustrated in FIGS. 3A and 3B, is provided to interrupt an induced current. According to the invention, such gap has a dimension of about 4 mm. While the gap may be enlarged to enhance the effect of interrupting the induced current, the shielding effect is correspondingly deteriorated. From this viewpoint, the gap should be dimensioned to be on the order of about 1 mm or larger but selected to maintain the desired shielding effect. The shield plate 11 may be provided with a lid 22 having a circular opening 21 through which the cylindrical infrared waveguide quartz column 3 is inserted.

To maximize an effect of infrared irradiation, a raising and lowering mechanism 9 vertically moves the infrared waveguide quartz column 3 so that the temperature may rise as rapidly as possible and the temperature may be distributed as evenly as possible. If the end surface 3 a of the infrared waveguide quartz column 3 smears, transmission of the infrared rays as well as rise of the temperature will be obstructed. To solve this problem, a quartz plate 13 is placed on the sample stage 10 and thereby prevents any impurities coming from the sample stage 10 to contaminate the end surface 3 a of the infrared waveguide quartz column 3. Taking into account the fact that the thermal treatment is carried out in various atmospheres, for example, vacuum, argon, nitrogen, helium or hydrogen, the components of the equipment directly serving for the thermal treatment are arranged within a vacuum chamber 4 which is provided with a vacuum pumping exhaust port 8 communicating with a vacuum pump and a gas inlet port 16.

Outside the shield plate 11, the coaxial double-walled cylindrical quartz tube 6 and cooling water tube 5 are provided to prevent the temperature in the vicinity of the sample stage 10 from rising excessively and destroying the equipment. The temperature of the sample can be measured by a thermocouple and an infrared temperature sensor, and the temperature can be controlled. There is provided a temperature sensor pickup port 14 for a lead wire of the thermocouple and a temperature sensor port 15 for the infrared temperature sensor. A temperature control circuit 23 is coupled to each of the quartz lamps 1 to the temperature sensors and to the RF coils 7 to control the temperature profile to which the sample is exposed, as shown, for example, in FIG. 6. The circuit 23 includes a suitable microprocessor programmed to control the temperature using conventional interface circuits between the microprocessor and the heating elements (1 and 7) and the temperature sensors. While a pair of the infrared lamps are provided one above other in the particular embodiment illustrated in FIG. 2, the placement of the infrared lamps is not limited to this embodiment. For example, the sample may be irradiated with infrared rays from two or three infrared lamps placed below the sample as illustrated by FIGS. 4(1) and 4(2); or from three infrared lamps placed above the sample as illustrated by FIG. 4(3); or from two pairs of infrared lamps placed above and below the sample, respectively, as illustrated by FIG. 4(4). Alternatively, the sample can be irradiated by a single infrared lamp placed above the sample and two infrared lamps placed below the sample as illustrated by FIG. 4(5); or from three infrared lamps placed above the sample and three infrared lamps placed below the sample as illustrated by FIG. 4(6). By tilting the quartz columns (i.e., mounting them off the vertical axis of FIG. 2), the number of the infrared waveguide quartz columns may be increased and thereby the area irradiated with infrared rays may be enlarged depending on a size of the SiC substrate to be thermally treated. Also for convenience of operation, particularly for the purpose of facilitating the sample 12 to be taken out, it may be selected whether the infrared lamps should be placed exclusively above the sample or exclusively below the sample.

FIGS. 5 and 6 plot a result of experimentally heating a 2 inch diameter SiC substrate. The experiments were conducted under conditions as follow: output of the infrared lamp: 100 V, 30 A (3 KW); output of high frequency: 14688 W; and frequency; 25.5 KHz. As for the atmosphere under which the thermal treatment was conducted, air pressure within the vacuum chamber was reduced to approximately 0.1 Pascal by a thermal-molecular pump and then argon gas was introduced into the chamber at a rate in the other of 1 L/min. The temperature was measured by an infrared temperature sensor mounted on the sample stage 12. In the case of heating by the high frequency wave alone (FIG. 5), it was found that the temperature of the sample is higher in its peripheral zone than in its central zone and the maximum temperature is approximately 1750° C. The thermal treatment temperature necessary for activation of the impurities being apt to become P-type impurities in SiC is normally in the order of 1800° C. and the desired activation can not be achieved at the temperature of approximately 1750° C. In addition, a differential temperature between the peripheral zone and the central zone of the sample was as remarkable as about 300° C. Such uneven temperature distribution inevitably makes electric properties of the SiC element uneven. Based on this observation, such method is practically unsuitable for mass production.

In the case of heating by the infrared lamps alone during less than 30 sec (FIG. 6), the maximum temperature was approximately 1000° C., which is insufficient to activate the impurities ion implanted into the SiC substrate. As opposed to the case of heating by the high frequency wave alone, the temperature of the sample was determined to be higher in the central zone than in the peripheral zone of the sample. Specifically, the differential temperature therebetween was approximately 600° C., which inevitably makes the electric properties of the SiC element and makes such method of thermal treatment unsuitable for mass production. After the sample had been maintained at a temperature lower than 1000° C. for 30 seconds using infrared heating, the high frequency heating was started. Thereupon, the temperature rapidly rose to a temperature of 1800° C. or higher after 40 seconds. In this way, the temperature reached a sufficiently high level to activate the impurities implanted into the SiC substrate. Approximately 10 seconds after completion of the about 40 second thermal treatment, the temperature was reduced to about 1200° C. or lower without any significant evaporation of Si from the surface of SiC. Consequently, appearing of irregularities on the surface of SiC was effectively restrained. Irregularities on the surface of the SiC substrate measured by an atom force microscope were substantially same as before the thermal treatment, i.e., the surface was adequately smooth. Significant irregularities would deteriorate electric properties of the SiC, such as pressure-resistance. The product obtained by use of the equipment according to the invention was observed to be free from such deterioration. The differential temperature between the peripheral zone and the central zone occurring in the thermal treatment at a temperature of 1800° C. was as minor as 44° C. and such minor differential temperature did not affect an in-plane evenness of the electric properties of the SiC element thermally treated by the equipment according to the invention. Based on the result of experimental measurement, the thermal treatment equipment according to the invention is suitable for mass production.

While the SiC substrate has been described and illustrated as an example of the sample, the sample is not limited to the SiC.

It will become apparent to those skilled in the art that various modifications to the preferred embodiment of the invention as described herein can be made without departing from the spirit or scope of the invention as defined by the appended claims. 

1. A thermal treatment equipment comprising: a chamber for allowing thermal treatment to be carried out in vacuum or various gas atmospheres; an electrically conductive sample stage positioned within said chamber for receiving a sample to be treated; a high frequency coil surrounding said sample stage; an infrared generator consisting of at least one infrared waveguide quartz column placed above or below said sample; an infrared lamp and a rotary elliptical reflector placed on one end of said infrared waveguide quartz column; a coaxial double-wall quartz tube placed inside said high frequency coil for receiving cooling water in said coaxial double-wall quartz tube; and wherein said infrared lamp is water or air cooled by cooling water or air flowing outside said infrared lamp.
 2. The thermal treatment equipment as defined in claim 1, wherein a quartz plate is interposed between a sample and said infrared waveguide quartz column.
 3. The thermal treatment equipment as defined in any one of claims 1 or 2, wherein a sample and said sample stage are covered with a shield plate.
 4. The thermal treatment equipment as defined in any one of claims 1 through 3, wherein said sample stage is covered with an electrically conductive shield plate provided with a gap having a dimension in a range of from about 1 mm to about 30 mm.
 5. The thermal treatment equipment as defined in any one of claims 1 through 4, wherein said sample stage is made of one of tungsten, molybdenum or tantalum.
 6. The thermal treatment equipment as defined in any one of claims 1 through 4, wherein said shield plate is made of one of tungsten, molybdenum or tantalum.
 7. The thermal treatment equipment as defined in any one of claims 1 through 4, wherein said sample stage is made of one of carbon or SiC coated carbon.
 8. The thermal treatment equipment as defined in any one of claims 1 through 4, wherein said shield plate is made of one of carbon or SiC coated carbon.
 9. The thermal treatment equipment as defined in any one of claims 1 through 8, wherein the high frequency wave has a frequency of less than about 50 kHz.
 10. The thermal treatment equipment as defined in any one of claims 1 through 9 and further comprising a mechanism adapted to adjust a distance between one end surface of said quartz column and a sample in a range of from about 0.5 mm to about 20 mm.
 11. The thermal treatment equipment as defined in any one of claims 1 through 10 and further comprising a sample temperature control means adapted to measure a temperature of one of the sample stage or a sample using one of a pyrometer or a thermocouple to thereby control the value of voltage or current applied to the infrared lamp or the high frequency coil.
 12. The thermal treatment equipment as defined in any one of claims 1 through 11, wherein said quartz column is tilted.
 13. The thermal treatment equipment as defined in any one of claims 1 through 12, wherein said equipment is programmed so that a SiC substrate is heated from a room temperature to about 1200° C. or higher in from about 10 seconds to about 5 minutes, then maintained at such temperature for about 10 seconds to about 10 minutes and thereafter the SiC substrate is cooled to a temperature lower than about 1200° C. in about 10 seconds to about 30 minutes.
 14. The thermal treatment equipment as defined in claim 13, wherein said equipment is programmed so that the SiC substrate is previously heated to a temperature lower than about 1200° C., then heated from a room temperature to about 1200° C. or higher in about 10 seconds to about 5 minutes and thereafter cooled to a temperature lower than about 1200° C. in about 10 seconds to about 30 minutes.
 15. Thermal treatment equipment comprising: a chamber for allowing thermal treatment to be carried out in vacuum or various gas atmospheres; an electrically conductive sample stage positioned within said chamber for receiving a sample to be treated; a high frequency coil surrounding said sample stage; an infrared generator consisting of at least one infrared waveguide quartz column positioned to direct infrared energy toward said sample; and a temperature control circuit coupled to said coil and said infrared waveguide quartz column and programmed to heat a SiC substrate from a room temperature to about 1200° C. or higher in from about 10 seconds to about 5 minutes, then maintained at such temperature for about 10 seconds to about 10 minutes and thereafter the SiC substrate is cooled to a temperature lower than about 1200° C. in about 10 seconds to about 30 minutes.
 16. Thermal treatment equipment comprising: a chamber for allowing thermal treatment to be carried out in vacuum or various gas atmospheres; an electrically conductive sample stage positioned within said chamber for receiving a sample to be treated; a high frequency coil surrounding said sample stage; an infrared generator consisting of at least one infrared waveguide quartz column positioned to direct infrared energy toward said sample; and a temperature control circuit coupled to said coil and said infrared waveguide quartz column and programmed so that said SiC substrate is previously heated to a temperature lower than about 1200° C., then heated from a room temperature to about 1200° C. or higher in about 10 seconds to about 5 minutes and thereafter cooled to a temperature lower than about 1200° C. in about 10 seconds to about 30 minutes. 